J. Biol. Chem., Vol. 267, Issue 33, 24023-24027, 11, 1992
Selective tissue distribution of G protein gamma subunits, including a new form of the gamma subunits identified by cDNA cloning
JJ Cali, EA Balcueva, I Rybalkin and JD Robishaw
Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania 17822.
The GTP-binding regulatory proteins (G proteins) that transduce signals
from receptors to effectors are composed of alpha, beta, and gamma
subunits. Whereas the role of alpha subunits in directly regulating
effector activity is widely accepted, it has recently been demonstrated
that beta gamma subunits may also directly regulate effector activity. This
has made clear the importance of identifying and characterizing beta and
gamma subunits. We have isolated a cDNA clone encoding a new gamma subunit,
referred to here as the gamma 7 subunit, using probes based on peptide
sequences of a gamma subunit previously purified from bovine brain. The
clone contains a 1.47-kilobase cDNA insert, which includes an open reading
frame of 204 base pairs that predicts a 68- amino acid polypeptide with a
calculated M(r) of 7553. The predicted protein shares amino acid identities
with the other known gamma subunits, ranging from 38 to 68%. Also
characteristic of gamma subunits is a carboxyl-terminal CAAX motif. The
expression of the gamma 7 subunit as well as the gamma 2, gamma 3, and
gamma 5 subunits was examined in several bovine tissues at both the mRNA
and protein levels. Whereas the gamma 2 and gamma 3 subunits were
selectively expressed in brain, the gamma 5 and gamma 7 subunits were
expressed in a variety of tissues. Thus, the gamma 5 and gamma 7 subunits
are the first G protein gamma subunits known that could participate in the
regulation of widely distributed signal transduction pathways.
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